Tape Sensing

The schematic below shows the circuit configuration for one of the three tape sensors (the same circuit simply needs to be replicated for each sensor). Each circuit has an LED part and a phototransistor part. The phototransistor is in sourcing configuration and its output is connected to a comparator in an inverting configuration. During empirical testing, it was found that there was a significant difference between values returned when the sensor was looking at the light background and the dark black tape.